Great Stuff Concrete Lift: The DIY Fix You’re Overlooking?

You see it every time you walk up your front path or pull into your garage. That one sunken concrete slab—a frustrating eyesore and a dangerous trip hazard. You’ve considered the back-breaking labor of mixing and pouring new concrete or the hefty price tag of hiring a professional crew. But what if there was a simpler, faster, and more affordable way to solve the problem yourself?

This is where the idea of a “Great Stuff concrete lift” comes in. Using expanding polyurethane foam, a method once reserved for professionals, is now accessible to determined homeowners. This guide will walk you through everything you need to know about this innovative technique, from understanding the root cause of your sunken slab to the step-by-step process of lifting it back into place.

Why Does Concrete Sink in the First Place?

Before you can fix the problem, it’s essential to understand why your concrete slab is sinking. Concrete is incredibly heavy and durable, but it’s only as stable as the ground beneath it. The most common culprits behind sunken concrete are issues with the underlying soil.

Over time, the soil can shift, compact, or wash away. Here are the primary causes:

• Soil Erosion: Water is concrete’s biggest enemy. Poor drainage, broken sprinkler lines, or improperly placed downspouts can wash away the soil supporting the slab, creating voids and causing the concrete to settle.
• Poor Compaction: When your home was built, the soil may not have been properly compacted before the concrete was poured. This leads to gradual settling over years as the ground naturally compacts under the immense weight of the slab.
• Tree Roots: Large, nearby trees have powerful root systems that can grow underneath concrete slabs. As they grow, they can lift the concrete, and if they die and decay, they leave behind voids that cause the slab to sink.
• Freeze-Thaw Cycles: In colder climates, moisture in the ground freezes and expands, pushing the slab upward. When it thaws, the soil contracts, and the slab settles back down, often unevenly.

Identifying the cause is the first step toward a lasting repair. A sinking slab isn’t just a cosmetic issue; it can lead to bigger problems like a large gap between your patio and house, which can compromise your home’s foundation over time.

What is Polyurethane Foam Concrete Lifting?

Polyurethane foam concrete lifting, also known as poly-jacking or foam leveling, is a modern method for raising and stabilizing sunken concrete. Professionals use a two-part polymer that is injected as a liquid through small, drilled holes in the concrete slab. When the two parts mix, a chemical reaction occurs, causing the liquid to expand into a high-density, structural foam.

This expanding foam fills any voids beneath the slab, re-establishes support, and gently lifts the concrete back to its original position. The foam is incredibly strong and lightweight—it won’t add significant weight to the already unstable soil, which is a major advantage over traditional methods like mudjacking.

While professional-grade systems use specialized equipment, the core principle has inspired DIY-friendly approaches using off-the-shelf expanding foam products like Great Stuff. It’s crucial to understand that canned foam sold for insulation is not the same as the high-density, two-part foam used by professionals. However, for smaller, more manageable jobs, it can be an effective and budget-friendly solution.

Can You Really Use Great Stuff to Lift Concrete?

This is the big question. Standard canned foam like Great Stuff Gaps & Cracks is not designed to be a structural lifting agent for heavy concrete slabs. Professional concrete lifting foam has a much higher density and compressive strength, specifically engineered to support immense loads. Using a low-density insulation foam for a heavy-duty job can lead to failure.

However, many DIYers have found success using this method for smaller, lighter slabs like sidewalk sections. The key is to mechanically lift the slab first using jacks, pry bars, or levers, and then use the expanding foam to fill the void and provide support. The foam itself isn’t doing the heavy lifting; it’s acting as a strong, durable, and waterproof support pillar once the slab is in place.

Attempting to use the foam’s expansion force alone to lift a heavy slab is risky and likely to fail. It can result in an uneven lift or simply won’t be powerful enough. For larger issues, such as trying to fix a dip at the end of your driveway, a professional assessment is often the safer bet.

The DIY Concrete Lifting Process: A Step-by-Step Guide

If you have a small, sunken sidewalk slab or patio stone and are ready to tackle the project, this method can save you significant money. Remember, safety first—always wear gloves and safety glasses when working with expanding foam.

Step 1: Assess the Situation and Gather Your Tools

First, confirm that your concrete slab is a good candidate. It should not be severely cracked or crumbling. This method works best on whole slabs that have sunken. If the slab is broken into many pieces, replacement is a better option.

Here’s what you’ll need:

• Heavy-Duty Pry Bars or a Bottle Jack: To mechanically lift the slab.
• Drill with Masonry Bit: To create injection holes.
• Cans of Expanding Foam: Choose a “Big Gap Filler” or similar high-expansion formula. Calculate the void space to estimate how many cans you’ll need. It’s better to have too much than not enough.
• Shovel and Trowel: For clearing debris and cleaning up.
• Safety Gear: Gloves, safety glasses, and old clothing (expanding foam is permanent).
• Wood Blocks or Shims: To temporarily support the lifted slab.

Step 2: Prepare the Area

Clear all dirt, weeds, and debris from around the edges of the sunken slab. This will allow you to see the full extent of the void and give you room to work. Use a shovel to dig out a small trench around the slab if necessary.

It’s also crucial to ensure the slab can move freely. Use a pry bar to check if the edges are caught on adjacent slabs. If so, you may need to clear the expansion joints to prevent binding and cracking during the lift.

Step 3: Drill Injection Holes

Strategically drill several holes through the concrete slab using your masonry bit. The holes should be about 5/8-inch in diameter, just large enough for the nozzle of the spray foam can. For a standard sidewalk slab, drilling one hole in each corner is a good starting point.

Drilling the holes beforehand allows you to quickly inject the foam once the slab is lifted, minimizing the time it has to be held in position.

Step 4: Lift the Concrete Slab

This is the most critical step. Do not rely on the foam to lift the slab. You must lift it mechanically first. Use your heavy-duty pry bars or a bottle jack to slowly and carefully raise the sunken edge of the slab until it is level with the surrounding surfaces.

Once the slab is at the desired height, use wood blocks or shims to secure it in place. This ensures the slab remains stable while you apply the foam and prevents it from settling before the foam cures.

Step 5: Inject the Expanding Foam

With the slab securely propped up, it’s time to fill the void. Following the manufacturer’s instructions, shake the can of expanding foam vigorously. Attach the nozzle and insert it into one of the pre-drilled holes.

Inject the foam steadily, moving from one hole to the next. The goal is to fill the void completely without creating excessive pressure. You should see the foam begin to expand and fill the space. You may see some foam seeping out of the edges, which is a good sign that the void is being filled.

Step 6: Curing and Finishing

Allow the foam to fully cure according to the product’s directions, which is typically 8-24 hours. During this time, the foam will harden into a rigid, supportive base. Do not remove the shims or put any weight on the slab until it has fully cured.

Once cured, remove the wood supports. The slab should now be firmly held in its new, level position. Use a utility knife or serrated blade to trim any excess foam that has squeezed out from the edges or injection holes. You can then patch the small holes with a concrete patching compound for a clean, finished look.

Pros and Cons of DIY Foam Jacking

Like any home repair method, using expanding foam for a concrete lift has its advantages and disadvantages. It’s important to weigh them carefully before deciding if this is the right project for you.

Advantages:

• Cost-Effective: Compared to professional poly-jacking or full concrete replacement, the DIY foam method is significantly cheaper.
• Fast and Convenient: The process can often be completed in a few hours, and the surface is typically ready for use the next day.
• Waterproof: Polyurethane foam is hydrophobic, meaning it repels water. This helps prevent future soil erosion under the slab.
• Lightweight: The foam adds minimal weight, preventing further soil compaction.

Disadvantages:

• Not for Large Jobs: This method is not suitable for large, heavy slabs like driveways or garage floors.
• Risk of Uneven Lift: It can be difficult to achieve a perfectly even lift, and over-lifting the slab is nearly impossible to reverse.
• Foam Strength: Canned insulation foam is not as strong as professional-grade lifting foam and may not provide long-term support in all situations.
• Messy Application: Expanding foam is incredibly sticky and can be difficult to clean up if you’re not careful.

Comparing Concrete Repair Methods

To help you make an informed decision, here’s a comparison of the most common concrete leveling and repair methods.

Method	Best For	Average Cost (Per Sq. Ft.)	Pros	Cons
DIY Foam Lifting	Small, lightweight slabs (e.g., sidewalks)	$1 – $3	Very low cost, fast, waterproof, DIY-friendly	Not for heavy loads, risk of uneven lift, lower strength
Professional Poly-Jacking	All types of slabs, including driveways and foundations	$5 – $25	Extremely strong, long-lasting, fast curing, minimally invasive	Higher upfront cost, requires professional installation
Mudjacking	Medium to large residential jobs	$3 – $6	More affordable than poly-jacking, uses natural materials	Heavy material can cause re-settling, larger holes required, can erode
Concrete Replacement	Severely cracked or spalled concrete	$8 – $20	Brand new surface, addresses underlying issues	Most expensive, disruptive, and time-consuming option

When to Call a Professional

While the DIY “Great Stuff concrete lift” is a clever solution for minor issues, it has its limits. It’s crucial to recognize when a problem is too big to handle on your own. You should call a professional concrete lifting company if:

• The sunken slab is part of your home’s foundation.
• You are dealing with a large or heavy slab, such as a driveway, garage floor, or large patio.
• The concrete is severely cracked or damaged.
• The sinking is significant (more than a few inches).
• You suspect an underlying plumbing or structural issue, such as a problem that might require a sill plate replacement.

Professionals have the right equipment and materials to do the job safely and effectively, ensuring a permanent solution. While the upfront cost is higher, it can save you from costly mistakes and further damage down the road.

Ultimately, tackling a sunken concrete slab with expanding foam is a viable option for the savvy homeowner with the right project. By understanding the process, respecting its limitations, and taking the proper precautions, you can restore safety and curb appeal to your property without breaking the bank.